Safety plug for flatirons



March 19, 1929. w r. HOQFNAGLE 1,705,524

SAFETY PLUG FOR FLATIRONS Filed Sept. 28, 1921 bun Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

WILLIAM T, HOOFNAGLE, 0F GLEN RIDGE, NEVI JERSEY, ASSIGNOR TO THE COMFO ELECTRIC IRON COMPANY, OF GLEN RIDGE, NEVI JERSEY, A CORPORATION OF NEW JERSEY.

SAFETY PLUG FOR FLATZROI-TS.

This invention relates to improvements in sat! by devices for preventing the overheating of electric flat irons. In carrying out the invention, I provide socket on or within the iron adapted to receive a plug which is outwardly the same as the threaded fuse plu commonly used for protecting house light circuits. The socket is open at the bottom and when the plug is threaded into the socket its base contact engages the body of the iron and is heated thereby when the iron in use. The plug has the usual side contact, in the form of a threaded shell, which engages a similar shell within the socket. lVithin the plug, I arrange a fusible elementadapted to melt at a relatively low temperz re, said ele ment, directly engaging the base contact and adapted to be melted by the heat of the iron when the latter is left standing with the current on and becomes dangerously hot. In addition to this fusible element, I provide, within the socket, a filament which can be heated to a dull red by the electric current while t ,e current is on, and serves as a visual signal to the operator, to indicate when the current is on or of. This filament and the fusible element are connected in series with the heating resistance and they may be connectcd in various ways with respect to one another. In the preferred arrangement, I provide in the plug an ordinary fuse wire capable of carrying the heating current for the. iron and of being fused by the heat of the iron when the latter is overheated, and I z rran e a lighting filament in parallel with Elli) wire. il ith this arrangen'ient, tl lilament, which is of more. expensive material than the fuse, can be made very small in cross section, since it is not designed for carrying the heating current for the iron. The filament can thus be inexpensively made, and be- -ause of the small quantity of current carried by the filament the heat developed by it in the plug is negligible. lVhen one plug burns out, it can readily be replaced by another of the same kind, or, in an emergency, by an ordinary fuse plu in the accompanying drawing,

Fig. 1 is a top plan view of a. flat iron, partly broken away, and with the upper cas ing and handle removed showing my invention applied thereto, the heating resistance being shown in dotted lines;

Fig. 2 is a section on the line 22 of F 1, sh owing the preferred form of safety plug;

. 3 is a vertical section through. a modi- 121 of plug; and,

4: is snmlar view showing another ,cation leferring to igs. 1 and 2 of the drawing, A represents the iron comprising a metal base 1, a heating resistance resting upon the base, and a metal body 3 which rests upon the heating element and is clamped to the base in the usual manner. One end of the resistanc is connected to terminal t and the other end is grounded on the body 3, at g. In the body 3 is a recess 4, within which is arranged a socket s, of insulating material, hav an internal annular threaded contact member 5. A hollow screw plug 5 is provided with a threaded side contact 6, for engaging the contact 5, and with a base contact 7, which, when the plug is in place, rests against the metal body lVithin the plug shown in Fig. 2 is arranged an ordinary fuse wire 8, of ample capacity to carry the heating current but adapted to fuse by the heat of the iron conducted through the base contact 7, when the iron becomes excessively hot. This fuse is connected in the usual manner between the side and base contacts of the plug, and in parallel with it, and similarly connected is a lighting filament 9, preferably of some nonoxidizable wire, such as platinum. This filament is proportioned so that it heats to a dull red when the current is on and serves as a signal to the operator, to indicate when the current is on. As the fuse has ample capacity for carrying the current required to heat the iron, and the current passing through the filament is not required for that purpose, the filament may be made very small in cross section and proportioned to carry a very small quantity of current. Thus the cost of the filament is slight and the heat generated in the plug by the current passing through the filament is negligible. The threaded contact in the socket is connected by a conductor 10 to the terminal t, and it will be evident that the current flowing through the resistance and the plug from one terminal to the other will flow in parallel through the fuse and filament.

lVith the device shown in Figs. 1 and 2, if the iron becomes overheated the fuse wire melts, and as this cuts off the main path for the current through the plug, the filament becomes heated and melts, thus cutting off the current entirely from the resistance.

In Fig. 3, I have shown an arrangement wherein a conductor 11, which may be of copper,is connected to the side contact 6 of the plug and to a body of fusible material, such as solder, which is mounted on the base con tact 7 and the filament 9 is connected in 1 L l a I parallel With a part of the conductor. \Vrth this arrangement, the copper Wire will carry the current for heating the iron, without itself becoming heated, and the filament, which may be made small in cross section, will carry enough current to cause it to become a dull red. Should the iron become overheated, the fusible connection 8 will melt and this will interrupt the flow of current between the conductor and the base contact of the plug.

In Fig. l, I have shown another arrangement wherein a conductor 12, of nonoxidizable material such as platinum, is connected to the side contact of the plug and to a body of fusible material 8 on the base contact.

In this case, the conductor 12 carries the current for heating the iron and the conductor is proportioned so that it will heat to a dull red and serve as a Visual signal when the current is on. If the iron becomes overheated, the fusible material melts and breaks the connection between the conductor and the base contact, thus shutting 01''? the current from the heating resistance.

lVhat I claim is:

I an electrically heated flat iron, a heating resistance, a metal body in series with the resistance adapted to be heated thereby, a socket on the iron adapter to receive a fuse plug, a hollow plug fitting said socket and having a base terminal engaging said body, and a fuse element and a lighting filament within the plug, said fuse element adapted to melt at a relatively low temperature and said element and filament being connected in series with said resistance.

In testimony whereof I atlix my signature.

WILLIAM T. HOOFNAGLE. 

